In general, a mobile phone is provided with a function of notifying a user of reception of a “no reply” signal (absent signal) when a call signal is received, but not responded to. For example, “absent signal received ” or another message may be displayed near the center of a standby screen, reception of an absent signal may be displayed by using a graphic referred to as a “pict” in a dedicated region of an upper portion or lower portion of the screen, or an LED or other light emitting device may be turned on to notify the user of the reception of the absent signal.
Further, when there is not only reception of call, but also reception of e-mail (reception of new mail), the reception of the e-mail is notified to the user by the same method as that in the case of a call.
The display of reception of an absent signal as described above is usually erased by the user performing a predetermined confirmation operation. For example, in the case of a call, the display is erased by displaying a screen of a call record, while in the case of e-mail, the display is erased by receiving new mail from a server and displaying that received mail on the screen. Even when the user performs an operation different from that, the display of the reception of the absent signal is not erased.
Further, in many mobile phones, buttons for directly shifting to the call record or mail reception screens are displayed as soft keys together with messages of reception of an absent signal. When a user depresses a button corresponding to this display to shift to these screens, the message of reception of an absent signal is erased from the standby screen.
But recently, the modes of communication of phones have become more diversified. Phones capable of performing, in addition to conventional audio speech by line switching, packet communication utilizing IP (Internet Protocol) networks are being widely utilized. For example, there is “chat mail” for performing conversation by mobile phones exchanging text in real time (see Patent Document 1). Chat mail is one of the modes of communication called as “group communication” where members who are registered in advance form a group and exchange text and other data in real time in the group.
Further, as one type of group communication attracting attention recently, there is the one called PTT (push to talk) or PoC (push to talk over cellular). In PTT, a plurality of communication apparatus forming a group engage in audio speech with each other according to VoIP (voice over Internet Protocol) (see Patent Document 2).
In PTT group communication, a user who desires to speak pushes a predetermined button (PTT button) which is provided at the communication apparatus whereby a request to speak of the user is transmitted to a server apparatus. The server apparatus receives the requests to speak from the communication apparatus and gives a right to speak to one communication apparatus. The communication apparatus given the right to speak transmits audio data of the user to the server apparatus, then the server apparatus transmits that audio data to the other communication apparatus all together. Due to this, the plurality of communication apparatus forming the group engage in audio speech in real time.
Further, a mobile phone performing PTT communication executes processing concerning PTT communication according to a PTT communication application program. This application program is manually started by an instruction of the user or is automatically started up when there is reception of a PTT signal (reception of notification of hosting PTT communication by an e-mail etc.)
Further, when the PTT communication application program is automatically started up in response to the reception of a signal, the reception of the PTT signal is informed to the user by a report sound etc. At this time, if an instruction of the user is input by operation of a speech button etc. so as to participate in the PTT communication, the application program transmits a reply indicating participation in PTT communication to the server apparatus and starts PTT communication. On the other hand, when the instruction of the user is not input for a predetermined time or longer, the application program autonomously ends without transmitting a participation reply.
Patent Document 1: Japanese Patent Publication (A) No. 2003-174520
Patent Document 2: Japanese Patent Publication (A) No. 2005-522067